1. Field of the Invention
The present invention relates to fuel injection control of an internal combustion engine and, more particularly, to control of fuel supply quantity from a fuel injection system by a model for the behavior of fuel, which is obtained by modeling the dynamic behavior of fuel.
2. Related Background Art
As apparatus for controlling the fuel supply to the internal combustion engine according to operating conditions, there is known control technology by a fuel behavior model to control the fuel injection system by setting a mathematical model describing the fuel behavior in an inlet system and calculating the mathematical model set from operating conditions and fuel conditions to simulate the fuel behavior, thereby determining a necessary fuel supply quantity.
An example of this technology is one disclosed in Japanese Patent No. 2705298. The Japanese patent describes that this technology is one of calculating a fuel state quantity in an intake pipe, based on an atomizing model for expressing a state quantity of fuel atomization and a wall flow model for assigning fuel deposit quantities according to an intake-pipe wall surface portion and an intake-valve surface portion, and it can enhance the control accuracy of injected fuel quantity.
The fuel quality needs to be taken into consideration in order to estimate the fuel behavior. However, gasoline commonly used as fuel for the internal combustion engines does not consist of a single component in fact, but it is a mixture consisting of many components of different carbon numbers, which are mixed in either of various component ratios. It is thus difficult to estimate the behavior of fuel accurately. For that reason, for example, the above-stated technology employs an approach of representing the fuel quality by some selected types of components and determining values of physical properties for a combination of the components.
However, this approach is approximation on the assumption that multi-component mixtures behave in the same manner, and does not allow us to estimate different behaviors of the respective components. In particular, the property of fuel adhering to the wall surfaces etc. also varies with occurrence of change in pressure and temperature in the intake pipe, which can affect the fuel behavior, but the above approach can not respond to this change and thus fails to properly estimate the fuel behavior, thus degrading the control accuracy of supplied fuel.
An object of the present invention is, therefore, to provide a technique of controlling the fuel injection in the internal combustion engine, using a fuel behavior model capable of properly estimating the fuel behavior in accordance with change in the property of adhering fuel on the wall.
In order to accomplish the above object, a fuel injection control apparatus, a fuel control method, and a fuel control program of an internal combustion engine according to the present invention are based on a technology of controlling a fuel supply quantity from a fuel injection system by making use of a fuel behavior model obtained by modeling dynamic behavior of fuel flowing from the fuel injection system into a cylinder of the internal combustion engine, wherein the fuel supply quantity from the fuel injection system is controlled by making use of the fuel behavior model as a combination of behavior models of a plurality of fuel components having different boiling points.
The present invention makes it feasible to estimate the fuel behavior, particularly the behavior of adhering fuel on the wall, more accurately by the combination of behavior models of the plurality of fuel components having the different boiling points, and thus can enhance the control accuracy of supplied fuel. The behavior models of the fuel components do not have to be prepared in the number of kinds of the components included in the fuel, but behavior models in the smaller number than it permit the fuel behavior to be estimated with hither accuracy than the conventional behavior model does; estimation can be effected well by preparing at least two types of models.
It is preferable further to detect a fuel quality by detecting a predetermined physical property and correct a component ratio of the plurality of fuel components in the fuel behavior model according to the fuel quality detected.
Since in this configuration the control is arranged to detect the change in the property of supplied fuel and vary the structure of the fuel behavior model according thereto, it becomes feasible to estimate the fuel behavior more accurately in accordance with the change in the property of fuel and thus to enhance the control accuracy of supplied fuel.
The present invention will be more fully understood from the detailed description given here in below and the accompanying drawings, which are given by way of illustration only and are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description.